Exaltation of Ketu also lies in Scorpio according to BPHS. It is nowhere elaborated which portion of Vrishchika is own sign and which portion is exalted. It is discussed below in a separate section.

When we have to deal with Rahu's or Ketu's fruits, we have to take the above verses of BPHS into account. But when their effects are compared with respect to the effects of other planets on Kumbha and Vrishchika, then Saturn owns Kumbha and Rahu owns no sign, and Mars owns Vrishchika and Ketu owns no sign. It is because Chaayaa Grahas do not overpower full planets.

I have tested both views regarding own sign of Rahu for a long time over a large number of charts, and that is why I support the original view of BPHS.

References in BPHS about Own Sign, Moola Trikona and Exaltation of Nodes

There are many astrologers who advocate that Rahu and Ketu do not own any sign and have no points of exaltation or moola-trikona (MT). There argument is that such traits of nodes are not mentioned in the Graha-swaroop-varnana chapter at the beginning of BPHS, hence later reference in Dashaadhyaay is interpolation.

First, let use find out how many times own sign, MT and exaltation of nodes are reported in BPHS. I am here citing from Chowkhamba ediction by Pt Devachandra Jha which is based on genuine manuscripts, unlike the online version which has no manuscriptal basis and is sourced to tampered version of Sitaram Jha translated later by Santhanam into English. Chapter number in online version is one less than I mention here, but even in the online version and in all other versions of BPHS, all the following references will be found.

Own sign of nodes in first mentioned in the section dealing with Chara Dashaa.

Next reference to Own signs, MTs and exaltations of nodes in in MD's Dashaa-phala-adhyaay's (chapter 48, or 47 in online version) verses 35-36 which give the most detailed description. It is said that "according to some others KAnya-Meena are own signs of nodes" but Parashara Ji does not accept it and gives his own views.

Third reference to own sign of Ketu occurs in Ketu's MD phala- verse-71 in chapter 48 (online 47).

Then, verse-42 in Charaadi-dashaa-phala-adhyaaya talks of same own sign of Rahu and Ketu as mentioned earlier in verses 35-6 of chapter 48.

Fifth reference is under Mars-MD's Rahu-AD verse-8 of chapter-55 (online 54) which mentions exaltation and MT of Rahu .

Sixth reference is under Jup-MD's Rahu-AD verse-69 of chapter-57 (online 56) which mentions own sign,exaltation and MT of Rahu .

Eighth reference is in same chapter's verse-63 which mentions exaltation and own sign of Rahu .

Ninth reference is under Ketu-MD's Rahu-AD verse-44 of chapter-60 (online 59) which mentions exaltation and own sign of Rahu.

Tenth reference is under Venus-MD's Rahu-AD verse-36 of chapter-61 (online 60) which mentions exaltation of Rahu.

Eleventh reference is under Venus-MD's Ketu-AD verse-65 of chapter-61 (online 60) which mentions exaltation and own sign of Ketu.

Can it be believed that so many references, having mutual consistency, are all interpolations ?

Ketu's Own Sign Versus Exaltation in Vrishchika

This last verse is very important : it clearly mentions that exaltation and own sign of Ketu are not the same ! But Dashaa-phala-adhyaay's (chapter 48, or 47 in online version) verse 36 states that "Ghata" (=Kumbha) is own sign of Rahu and "Aalee" is exaltation of Ketu. All commentators translate "aalee" as Vrishchika or scorpio, and Charaadi-dashaa-phala-adhyaaya also mentions the same. Therefore, exaltation and own sign of Ketu are in different portions of same sign Vrishchika. It is nowhere mentioned which portion of Vrischika is exaltation and which is own sign of Ketu, but it is not difficult to find out, because Graha-swaroopa-adhyaaya of BPHS clearly states that all own signs of all planets are in latter halves of their respective signs. Therefore, Ketu's own sign is in latter half of Vrishchika, and exaltation is in first half of Vrishchika. Exact dividing line is hard to guess, because different planets have own sign from last 10 to last 18 degrees. Hence, we can take the average and put the dividing line at the middle of Vrishchika approximately, before which is exaltation of Ketu and after which is own sign of Ketu.

Now, the question arises why the own sign, MT and exaltation of nodes are mentioned only in Dashaa chapters of BPHS and not in the initial portion where these attributes of other planets are listed. The answer is simple : since the exaltation, MT and own signs of shadow planets (chhaayaa grahas) are also owned by other planets, nodes exhibit the fruits of ownership &c only during their dashaas when planets gets their full share of power. While analyzing overall fruits of a birthchart for lifelong characteristics, the own signs, MTs and exaltations of nodes are suppressed by other planets which have greater control over those signs. But even there, the functional beneficence and maleficence of nodes gets affected by their sign ownership.